Air damper

ABSTRACT

An air damper is formed with first and second sets of extruded aluminum blades pivotally mounted in a frame formed of extruded aluminum frame members with longitudinally extending channel means of different widths along the longitudinal edges of the respective blades. The different width channel means nest in a sealing relationship with one another and seal with the frame when the blades pivot to a closed position from an open position. The method of manufacture of the air damper includes the steps of severing predetermined lengths of blades and frame members from long aluminum extrusions preshaped for the blades and frame members, partially erecting a frame from frame members, alternating and pivotally mounting the first and second blades in the partial frame, completing the frame, and interconnecting the first and second blades with a linkage means to close the narrower width channel means first with the frame and then to follow and close thereon the wider width channel means to provide the nested sealing relationship between the blades of the first and second sets.

United States Patent 1191 Tarnoff Feb. 26, 1974 AIR DAMPER [57] ABSTRACTInventor! Sherwin Tal'lloff, NOTIhbPOOk, An air damper is formed withfirst and second sets of extruded aluminum blades pivotally mounted in a[73] Asslgnee' Balance Chicago frame formed of extruded aluminum framemembers [22] Filed: Mar. 30, 1972 with longitudinally extending channelmeans of different widths along the longitudinal edges of the respec-[21] Appl 239659 tive blades. The different width channel means nest ina sealing relationship with one another and seal with [52] US. Cl.98/110, 98/l2l the frame when the blades pivot to a closed position [51]Int. Cl F 24f 13/00 from an open position. The method of manufacture of[58] Field of Search 98/ l 10, 121 the air damper includes the steps ofsevering predetermined lengths of blades and frame members from long[56] References Cited aluminum extrusions preshaped for the blades andUNITED STATES PATENTS frame members, partially erecting a frame fromframe 3,017,899 1/1962 Goldsmith 98/110 members alternating and Pivotanymounting the first 3,191,241 6/1965 Johnson 93/1 10 and second blades inthe partial frame, completing the 3,261,373 7/1966 Ridenour 98 1 10frame, and interconnecting the first and second blades 3,447,443 6/1969Silvey 98/1 10 with a linkage means to close the narrower width3,484,990 12/1969 Kahn 98/121 channel means first with the frame andthen to follow Primary Examiner-Meyer Perlin Attorney, Agent, orFirm-Fitch, Even, Tabin &

and close thereon the wider width channel means to provide the nestedsealing relationship between the blades of the first and second sets.

Luedeka 10 Claims, 8 Drawing Figures /5.3 s 154 PATENTEBFEBZBHH SHEET 1OF 3 PATENTEDFEBZEIQH 3,793,932

SHEET 3 OF 3 Fig. 7

Fig, 8

SEVER sEvER E EXE 'E ASSEQABLE 1ST BLADE. 2ND BLADE MEMBER PARHALEXTRUSION EXTRUSION EXTRUSlON FRAME ADHERE PIVOTALLY COMPLETE gi fg ggsEALs o MOU-NT FRAME NEST 8 BLADES BLADES ASSEMBLY SEAL AIR DAMPER Thisinvention relates to an air damper having a series of pivotally mountedblades which are movable between an open position in which the air mayflow through the damper and a closed position in which air issubstantially blocked from flow through the air damper.

Air dampers used in air modulating systems are often placed in an airduct with the blades being pivoted to control the flow rate of cool orhot air through the damper and with the damper blades adapted to bepivoted to a closed position to substantially block air flow through theduct. In US. Pat. No. 3,381,601, an air damper of this general kind isdisclosed with a set of air damper blades pivotally mounted at theiropposite ends to side members of a frame for turning to a closedposition in which side edge portionsof the damper blades overlap shelveson the side frame membersto provide side seals withthe frame uponoperation of a blade actuator. The damper blades carry flexibleresilient seals along their longitudinally extending edges for providinga seal between blades and with shelves on the top and bottom framemembers. Thus, in a closed position the air flow opening for the airthrough the damper may be substantially blocked by the blades and theircooperation with the encircling frame.

The amount of air leakage through an air damper of this kind when theblades are in a closed position is an important criterion. For example,some specifications for air dampers of this kind require that theleakage be less than 0.75 percent of the maximum air flow through thedamper when it is in a fully open position. Such air tight sealing isdifficult to achieve and maintain for dampers mass-produced on a largecommercial scale without the use of expensive resilient seals all aroundthe frame. Even with such frame carried seals, leakage may still occurdue to warped or bent damper blades which provide an imperfect sealbetween adjacent edges thereof. More specifically, damper blades formedof sheet metal of the usual thickness for damper blades are relativelyflexible and when exposed to high static pressure on the blades over thewide area of the blades will bend and deflect at the center thereof froma sealed position particularly with the top or bottom of the frame. Forexample, two inches of static pressure for a 48 inch long blade, mayresult in as much as 600 pounds of force over the entire area of thedamper with the result that the sheet metal damper blades often bendsubstantially in the center portion of the length of the blades.

Additionally, it is difficult to fabricate straight, unwarped damperblades from sheet metal stock which is roll formed while in a long stripand subsequently severed to form a number of blades. These long stripsof sheet metal are prestressed when rolled to complex blade shapes. Thenwhen a blade length is severed from the strip, the blade length bends orwarps as the stresses are free of restraint. Moreover, such bladebending operations result in rather expensive blade to manufacture.

Another problem with prior art damper constructions was that assembly ofthe blades and dampers was too difficult and complex for unskilled laborwith the result that the blades and seals were not always properlyoriented and in the proper sequence. Also, resilient seals of complexshapes were expensive and had to be correctly correlated relative toeach blade and to the frame during assembly. Moreover, the various kindsof blades, the different kinds of seals as well as different blades forvarious widths and heights of dampers often required a complex andexpensive inventory of frame members and damper blades.

Accordingly, a general object of the present invention is to provide anew and improved air damper. Another object of the invention is toprovide an air damper formed with extruded aluminum damper blades, whichhave a unique shape to resist bending and which seal readily with anextruded aluminum frame and with one another, and formed with extrudedaluminum frame members for manufacture and assembly at a competitive andlow cost.

Other objects and advantages of the invention will become apparent inthe following detailed description taken in connection with theaccompanying drawings in which:

FIG. 1 is a perspective view of an air damper with one side frame memberpartially broken away and embodying the novel features of the invention;

FIG. 2 is an enlarged vertical cross-sectional view of the air damper ofFIG. 1 but with the damper blades in an open position;

FIG. 3 is a perspective view of a damper blade of a first kind used inthe air damper of FIG. 1;

FIG. 4 is a sectional view generally similar to the view of FIG. 2 butwith the blades in a closed position;

FIG. 5 is a perspective view of a damper blade of a second kind used inthe air damper shown in FIG. 1;

FIG. 6 is an enlarged fragmentary perspective view of a means forpivotally mounting the blades to a side frame member;

FIG. 7 is a rear view of the air damper partially in section and showingthe damper blades in a closed position; and

FIG. 8 is a block diagram of a method of constructing the air damperillustrated in FIG. 1.

As shown in the drawings for purpose of illustration, the invention isembodied in an air damper unit 11 of the kind which may be used in anair modulating system and which may be inserted into an air duct (notshown). Very generally, the air damper 11 comprises a frame 14 having atop frame member 15 and a bottom frame member 16 which are disposedparallel to one another and spaced from each other by a pair of sideframe members 17. The frame members 14, l5, l6 and 17 are joined to oneanother to form the enclosed frame 14. The frame 14 encloses a centralopening 18 through which air may flow in the direction shown by thearrow A. Air flow through the damper is controlled by a series of firstand second air damper blades 20 and 21 which are pivotally mounted atthe opposite ends thereof by pivot means 22 to the opposite sidememebers 17 for turning substantially simultaneously between a fullyopen position, such as shown in FIG. 2, in which the damper blades 20are substantially parallel to the direction of air flow through thecentral opening 18 in the frame 14 and a closed position in which theblades 20 and 21 block air flow through the central opening 18. In theclosed position, the blades 20 and 21 are generally aligned withlongitudinally extending edges thereof in sealed engagement with oneanother and with the remote longitudinal edges of the top and bottomblades in sealed engagement with shelves 27 and 28 projecting inwardlyfrom the top and bottom frame members and 16. Side edges of the bladesand 21 also abut shelves 29 projecting inwardly from the respectivevertical frame side members 17 to provide side seals between the bladesand the frame.

Air damper constructions of a kind similar to that described above aredisclosed in US. Pat. No. 3,381,601 with damper blades made of sheetmetal, which dampers are generally satisfactory, but have theshortcoming that the sheet metaldamper blades may be warped and bentand,without corrective measures, unable to provide a good tight sealwith the frame and with one another to meet rigid specificationrequirements, e. g., a

leakage of less than 0.75 percent of the maximum air flow through thedamper. These prior art sheet metal blades are generally formed byrolling long lengths, e.g., 18 foot lengths, to the blade shape and thencutting lengths of blades therefrom. Upon cutting the rolled formedstrip into blade lengths, the blades often warp or twist due toprestresses in the steel strip caused during the roll forming andreleased by the severing operation. Further, the blade shapingoperations are relatively expensive. Moreover, sheet metal blades of thethickness used are relatively flexible under large static loadconditions and they tend to bend and deflect relative to the frameparticularly at the top and bottom shelves 27 and 28 allowing airleakage beyond that permissible. Also, such damper blades of the priorart employ relatively complex resilient seals which are expensive andrequire a definite and complicated assembly relationship to assureproper sealing.

In accordance with one aspect of the present invention, air leakageexperienced heretofore may be reduced substantially by the use ofuniquely shaped damper blades 20 and 21 formed of extruded aluminumhaving reinforcing rib means 31 thereon which provide rigidity to resistbending and having longitudinally extending channel means 33 and 35 fornesting in a sealing relationship with one another when the damperblades 20 and 21 are in the closed position. The extruded aluminumblades 20 and 21 may be cut from long lengths of extrusions, but theextruded aluminum strips and damper blades are free of the prestresseswhich warp and bend the blades when they are separated from the stock asexperienced when cutting prestressed steel blades from a roll formedstrip of steel. Also, the roll forming operations used to shape thesheet metal blades are eliminated. The aluminum damper blades 20 and 21also are made of a dead metal, i.e., less resonant, and hence make lessnoise when hit by a metal object carried by the air stream; and thealuminum damper blades have less tendency to flutter or vibrate undercertain air flow conditions which tend to vibrate or flutter the moreresonant sheet metal blades.

To achieve an overlapping and nesting relationship for the channel means33 and 35, the illustrated channel means 33 is formed with a narrowerwidth than the channel means 35 and the blades are positioned in theframe to overlap and nest the narrow channels means 33 in the widerchannel means 35. Preferably, flat strip resilient seals 39 and 40 arecarried in each of the respective channel means 33 and 35 for sealingengagement with the top and bottom shelves 27 and 28 and also with thechannel means of an adjacent blade in a nested relationship therewith.The flat strip seals 39 and 40 are less expensive than the complex sealsof the prior art, and are preferably adhesive-backed for ready adhesionto the channel means. The nested channel means 33 and 35 provide asufficient seal between blades for many uses of an air damper withouthaving the resilient seals 39 and 40, as only a small tortuous passageexists between the channel means 33 and 35 when the blades 20 and 21 arein the closed position. Preferably, each of the narrow channel means 33has a resilient seal 39 even though it is only the uppermost blade inwhich the seal 39 actually seals against the shelf 27, and even thoughthe other seals 39 seal only at their ends against the shelves 29. Thisallows the assembly of the blades to be made fast without concern as tothe blade being a top or bottom or rightor lefthand blade.

Also, in accordance with an important aspect of the invention, airdampers 11 of various dimensions may be constructed by severingdifferent lengths from the frame extrusions for the frame members 15, 16and 17 and from the damper blade extrusions for the damper blades 20 and21 with the result that only a small inventory of blades or framemembers need be maintained irrespective of the height or the length ofthe damper. For instance, the illustrated air dampers have been madewith 7 to 48 inch blade lengths and with two to nine damper blades inthe damper. As will be explained in greater detail, the aluminumextrusions for the damper blades are made in relatively long lengths,for example, 20-foot lengths, with the individual blades being severedfor the desired blade length from the 20- foot extrusions.

Preferably, the channel means 33 and 35 have a rectangular cross sectionto allow nesting and to permit ease of insertion of and fastening of theseals 39 and 40 to a bottom wall in the channel means. The illustratedresilient seals 39 and 40 have an adhesive coating covered by a backingstrip (not shown) which is peeled from the adhesive coating prior toinserting the seals to adhere to the bottom channel walls 43. In thismanner, the seals may be readily applied to the damper blades in a quickand economical fashion.

Because unskilled labor is often used, the assembly of the damper ismade simple and relatively error free by the use of damper blades whichare symmetrical about their pivot axis with identical channel means 33or 35 on opposite edges of the same blade so that each blade may be usedeither as a top, bottom or intermediate blade. The manufacture of thedamper is economical in that the number of operations is few andcomprises the following steps: severing the long extrusion to formblades 20 of a predetermined length; severing another long extrusion toform blades 21 of a predetermined length; severing a long frameextrusion to form the desired lengths for the frame members 16, 17 and18; joining the top and bottom frame members to a side frame member toform a partial frame; alternating and pivotally mounting the blades 20and 21 in the frame and completing the frame; and adjustablyinterconnecting the blades with the channel means 33 of the blades 20nesting in the channel means 35 of the blades 21 and with the top andlower blades sealing with the top and bottom shelves 27 and 28 and theside edge margins of the blades sealing with the side frame members 29.In the preferred embodiment, the seals 39 and 40 are adhered to theblades after the blades are severed from the extrusions.

Referring now in greater detail to the damper blades 20 and 21., theyare severed from a long blade extrusion at transversely extending bladeends 45 and 47 with a length greater than the distance between inwardlyfacing vertical edges 49 of the respective side frame shelves 29 so thatmarginal edge portions 50 of the blades may abut the shelves 29 toprovide vertical side seals when the damper blades are in a closedposition. To allow pivoting of these long blades, the side frame shelves29 are provided with cut outs or openings 51 to receive central offsetsections 53 of the damper blades, the offset sections 53 cooperatingwith pivot means 22 including a slotted stub shaft or pin 57 forpivotally mounting the blades to the side frame members 17.

Reinforcing rib means 31 reinforce the offset blade sections 53 againsta tearing of the metal due to torques applied through the slotted pin 57(FIG. 6). More specifically, the slotted pin 57 has a slot 59 forreceiving a central web 61 of the blade offset section 53. With theslotted pin 57 mounted on the blade web 61, the pin is centered betweena pair of oppositely directing and outwardly projecting ribs 63 of therib means 31. Preferably, the ribs 63 are rectangular in cross section,extend longitudinally of the blade, and have a height less than theheights of the respective channel means 33 or 35 so that the reinforcingribs 63 will not substantially interfere with air flow across theblades. The reinforcing ribs 63 are disposed at an angle to the planesof the respective wide planar section or halves 65 and 66 of the blades.

It can be appreciated from the examination of the damper blades and 21that opposite planar sections 65 and 66 of the blades are offsetrelative to a vertical plane taken through the longitudinal pivotal axis69 (FIG. 3) so that each damper blade may seal on the respective forwardand rearward sides of the shelves 29 as clearly shown in FIG. 4. Asillustrated in FIG. 4, the upper planar section 65 may seal thedownstream (hereinafter called rearward) side of the shelves 29 whilethe lower planar section 66 may seal with the upstream (forward) side ofthe shelves 29. Thus, it will be seen that the offset blade section 53allows the pivotal axis 69 of the blades to intersect the shelves 29 andthe planar sections 65 and 66 to overlap their marginal edge portions 50with the forward and reverse sides of the shelves 29.

The channel means 33 and 35 are formed along the longitudinal edges ofthe planar sections 65 and 66 to nest with one another and to seal withthe top shelf 27 and the bottom shelf 28. The nested relationshipbetween the channel means 33 and 35 is achieved by a formation of thenarrow channel means 33 with a width less than the width dimension ofgroove 73, as best seen in FIG. 5, defined between parallel side walls87 and 88 for the channel means 35 of the damper blades 21. The bladesare positioned in the side frames and the dimension of the blades 20 and21 are such that the channel means 38 will be centered and be disposedwithin the groove 73 of the channel means 35. For instance, the bladesmay have about 5% inch widths with the blades being pivoted at 5-inchcenters to provide the overlap and centering of the respective channelmeans. The general rectangular cross section for the grooves 73, asdefined by the side walls 87 and 88 and the bottom wall 43, facilitatesthe installation of the inexpensive flat strip resilient seals 39 and40. While the illustrated embodiment of the invention uses resilientseals 39 and 40 such as of a closed cell neoprene, the seals 39 and 40may be eliminated where the leakage requirements are not a controllingconsideration. Thus, it is within the purview of the present inventionthat the nested channel means 33 and provide a sealing relationshipbetween longitudinally extending blade edges with or without the seals39 and 40.

In the illustrated embodiment of the invention, the wide seals in thewide channel means 35 are formed with a thickness considerably less thanthe depth of the receiving groove 73 to allow the bottom wall 43 of thechannel means 33 to enter into the groove 73 before abutting the wideseal 40. When the bottom damper blade has a wide seal, it is preferredto make the lowermost seal 40a (FIG. 4) of a thickness greater than thedepth of the groove 73 so that the seal will project out wardly of thegroove 73 to abut the lower shelf 29 and be compressed when in sealingengagement therewith. This thick lower seal 400 may be constructed asone integral layer or by superposing two layers of the wide seal 40 inthe groove.

On the other hand, the narrow seals 39 all are sufficiently thick toproject from the bottom wall 43 outwardly of the groove 73 to abut thetop shelf 27 (or a bottom shelf 28) and to be compressed slightly whenin sealing engagement with one or the other of the shelves 27 or 28. Itis to be understood that, when there are an odd number of damper blades,the lowermost blade will carry a narrow seal 39 for abutting the lowershelf 28. In the illustrated four blade construction, as shown in FIG.4, a wide seal 40a abuts the bottom shelf 28. A narrow seal 39 ispreferably inserted into the channel grooves 73 for each of the damperblades 20 so that they may be assembled without regard to whether or notthe blade will actually be a top, an intermediate or a bottom blade inthe series of blades 20 in the damper. Also, the narrow seals 39 in themarginal edge portions of the blades abut the overlapped portion of theside frame shelves 29 and prevent air from flowing into the end of thegroove 73 and past the corner of the shelf 29. The symmetry of theblades allows them to be used either as right-hand or left-hand bladesas narrow channel means 33 are the same size, located equidistantly fromthe pivot axis, and spaced the same distance from a plane through thepivot axis 69 and parallel to the planar sections and 66. The same isalso true of the symmetry for damper blades 21. The symmetry of theblades also provides a balanced blade which allows a balanced flow ofair between blades and affords a less turbulent flow of air through thedamper and duct. The balancing of the blades also reduces the net torqueexerted by the air stream on the blades resisting opening or closing ofthe blades.

The illustrated damper has been built in various sizes from a unit only7 inches wide to a damper measuring 48 inches by 48 inches. Theillustrated blades 20 and 21 are usually about 5 /2 inches wide with thepivot axes 69 spaced at about five inch centers. When the height of theduct is different from that of a multiple of blades, then the upperplanar section 65a (FIG. 4) is made wider than its lower planar section66 so that its channel means 33a will seal with the shelf 27a (as isshown by the phantom line) in FIG. 4. Thus, the top blade will not besymmetrical about the pivot axis in some instances. However, thebalancing of the top blade is not as critical as less air flows alongthe top of the damper.

To assure ease of opening from and closing of the channel means 33 and35 into the nested relationship and sealing of all blades with the frameshelves 27, 28

and 29, the damper blades 20 and 21 are interconnected by a linkagemeans 92 and adjusted to be timed in their rotation. In this connection,each second blade having the wide channel means 35 is swung away fromits associated nesting small channel means 33 slightly before the latterpivots from its closed to its open position. It is preferred that thesecond blade 21 from the top always be the power blade, that is, theblade which is driven by a suitable power or actuating means 90 such asmanual crank, a chain operator, apneumatic operator, an electricsolenoid, or an electric motor. Usually the actuating means is connectedto an elongated slotted pin or operating shaft 57a (FIG. 7) whichextends outwardly through an opening 91 in the side frame member 17 andalso through the air duct wall (not shown) to where the actuating means90 is usually located. Thus, the actuating means 90 may turn the pin 57ato exert a turning torque on the power blade 21.

The preferred interconnection between the power blade 21 and theremaining damper blades 20 and 21 includes an adjustable linkage means92 which is readily adjustable to assure that the side edge marginalportions 50 of all the blades will simultaneously be abutting or closelyadjacent the side frame members when the power blade is turned by theactuating means 90 to a sealing position with the side frame shelves 29.In this instance, the power blade 21 and the other blades 21 turnthrough approximately 90 between their open and closed positions whereasthe blades 20 move through approximately 87 between open and closedpositions. The opening and closing of all the blades appears to besubstantially simultaneous to an observer of the operation. A stop meansfor limiting the pivotal movement of the blades at the full openposition may be provided on the exterior of the damper for abutment tolimit the turning of the actuating means 90. Of course, the blades maybe opened to any lesser extent and this will proportionally reduce theflow rate of air through the damper from the maximum flow rate.

With the illustrated linkage means 92, the second or power blade 21drives the top or first damper blade 20 which in turn is connected tothe third blade 20 having a narrow channel means 33. The third bladewould then be connected to a fifth blade when one is present. The first,third and fifth blades all belong to one set of blades 20 while the evenblades belong to the other set of blades 21. Thus, the second blade isalso connected to the fourth blade to pivot it; and the fourth bladewould be connected to the sixth blade by similar means when a sixthblade is present. In this instance, the first set of blades 20 pivot ina direction (counterclockwise in FIG. 2) opposite to the direction(clockwise) the second set of blades 21 pivot when swinging to theclosed position.

The portion of the linkage means 92 extending be- I tween the' powerblade 21 and first blade 20 comprises a bracket 95 preferably made ofaluminum and fastened by aluminum rivets 96 to the rear side of theupper planar blade section 65. The bracket 95 includes an outwardlyprojecting flange 97 which is apertured to receive one end of a swivel101 .which is freely tumable in the aperture in the bracket flange 97.The swivel has a large diameter body 98, as best seen in FIGS. 4 and 7,joined at a shoulder to a small diameter end 99 and asnap retainer ring100 is fastened to thesmall diameter end. The swivel 101 is providedwith adiametrically extending bore to receive a lower end of aconnecting shaft 103 which is secured against sliding through the boreby a set screw 102 threaded in an axially extending bore in the swivel.The inner end of the set screw 102 may abut against the shaft 103 whenthe set screw is turned sufficiently into the threaded bore in theswivel. In a similar manner, the upper end of the shaft 103 is connectedto a swivel 104 which is identical to the swivel 101. The upper swivel104 for the first blade 20 is joumalled to turn in an aperture of anL-shaped flange 107 of a bracket 108 which has another flange 109, asbest seen in FIG. 4, fastened by suitable rivets to the upper planarsection 65 of the first blade.

To assure that both the upper and power damper blades have their edgemarginal portions 50 in contact with the shelves 29 when the power bladeis in the closed position, both of the damper blades may be'pivoted totheir closed position with the marginal edge portions 50 abutting theshelf 29 and then the set screws 102 are tightened in the swivels 101and 104 to lock the shaft 103 at a predetermined angle and at apredetermined effective length for the shaft 103 between the set screws.The shaft 103 will thus maintain given angular relationship andpositional relationship between the first and second blades to assurethey both are synchronized in movement and will both close together.

To prevent interference between channel means 33 and the channel means35, the blades 20 carrying the narrow channel means and having thenarrow outward projecting portion (bottom wall 43), as best seen in FIG.4, projecting from the side shelf 29 are swung through their final fewdegrees of closing and into the closed position abutting the shelves 29before the wide channel means 33 swings through its final degrees ofclosing and into the nested relationship with the closed narrow channelmeans 33 and against the shelves 29. If both channel means 33 and 35were simultaneously closing at the same time and at the same rate towardthe shelves 29, they would strike each other and inter fere with thenesting.

The relationship of shaft 103 and the pivot axes of the swivels 101 and104 in their respective brackets and 107 relative to pivot axes 69 forthe power blade 21 and the top blade 20 is such that the blade 20 mayfirst abut the side shelves 29 and fix the location of the axis for theswivel 104 while the swivel 101 is traveling through a few more degreesin a path substantially tangential to an are having its center at theaxis of the swivel 104 and a radius equal to the effective length of theshaft 103. The play and looseness in the mountings of the swivels 101and 104 in their respective brackets and the play and looseness in themountings for the damper blades 20 and 21 allow these movements withoutany binding.

Conversely, when pivoting to the open position, the pivot pin 57a willturn the power blade 21 through a short arc, e.g., 3 with the swivel 101again moving along a path substantially tangential to the are beingswung by the lower end of the shaft 103 at the axis for the swivel 101about its upper end at the pivot axis of the swivel 104. After the widechannel means 35 travels through several degrees and uncovers the narrowprojection formed by the bottom wall 43 of the narrow channel means 33,the swivel 101 moves from the tangential path and begins to pull theshaft 103 down and toward the shelf 29 thereby pivoting the narrow seals39 from shelves 29. As will be explained, the power blade 21 isconnected to the other blades 21, so that they also move in a similarmanner relative to the blades 20, that is to open before the blades 20and to follow and close behind the narrow channel means on the blades20.

To assure simultaneous opening and closing of the third damper blade 20with the first damper blade 20,

a means similar to that above described is provided. Briefly, anangle-shaped bracket 111 projects outwardly from a blade section 65 ofthe first blade 20 and has a flange fastened thereto by rivets 113. Theangleshaped brackets extend downstream and carry a swivel 114 similar tothe swivel 100 described above. A shaft 1 extends between the upperswivel 1 l4 and a similar swivel 117 mounted in an aperture on a bracketarm 1 19 fastened to the upper planar section 65 of the third blade byrivets 121. The effective length of the shaft 115 and its angularrelationship to the blades may be adjusted and the set screws 102tightened in the swivels 114 and 117 to assure that in the closedposition the overlapping marginal portions 50 of the third damper bladeabut the shelves 29.

The power blade 21 is connected to the fourth damper blade 21 in amanner generally similar to that described for the first and thirdblades 20. More specifically, as best seen in FIGS. 2 and 4,angle-shaped brackets 127 are riveted to the lower planar section 66 ofthe power blade and carry a swivel 129. A shaft 132 extends downwardlyfrom the swivel 129 to another swivel 133 carried on an angle-shapedbracket 135 riveted to the planar section 66 of the fourth damper blade.Thus, the effective length of the shaft 132 and its angularrelationships with the second and fourth.

blades between swivels 129 and 133 can be adjusted with tightening ofthe set screws 102 to assure closing of the fourth damper blade. Theseadjustments also assure proper positioning of the swivels, brackets andconnecting shafts for the blades when in the blade open positionillustrated in FIG. 2.

As stated above, the illustrated frame means 14 may be made in variouslengths such as, for example, 7 to 48 inches. Also, it is preferred thatthe frame side members 15, 16 and 17 be identical in cross section andbe severed from a long aluminum extrusion thereby reducing the requiredinventory for producing frames of various sizes. By way of example only,illustrated frame members 15, 16 and 17 are formed of a l2-gauge thick(.081 inch) wall thickness for extrusion body 141 which has a width ofabout 3% inches. Preferably, the extruded frame body 141 is formed witha front inturned flange 143 and a rear inturned flange 145providing-additional strength for the frame. Each of the frame membershas an identical size and shape for its respective shelf 27, 28 or 29which is integral with the extruded frame body 141. The frame members 17used for the sides have their shelves 29 suitably notched to provide theopenings 51 to receive the pivot means 22 and offset portions 53 of thedamper blades. The frame members are also pierced for the opening 91 andto receive rivets, as will be explained.

Each of the frame members 15, 16 and 17 is provided with a mitered end146, as best seen in FIGS. 1 and 7, for abutment with another miteredend to form the gen erally rectangularly-shaped frame. The frame membersmay be bent to form integral corners; but are preferably joined togetherin the corners by a means such as 10 interiorly disposed angles 149preferably made of aluminum and joined by aluminum rivets 151 to theside members at the corners. Also, the frame members may be butt weldedrather than joined by the illustrated angles 149. In this instance, twoangles 149 are provided at each of the four comers of the frame andlongitudinally extending grooves 153 are formed in the outer sides ofthe extrusion body 141 to receive the rivet heads so that the rivetheads will not project beyond outer flat surfaces 154 of the damperframe and interfere with sliding the damper into a close fitting airduct.

Referring now in greater detail to the pivot means 22, the slotted pin57 is preferably joumaled in a stationary, sintered, oil-impregnatedbearing 159, as best seen in FIG. 6. The bearing is generally ellipticalin shape with upper and lower slots 161 for receiving in slidingengagement portions of the shelves 29 at the notches 51. The bearingsare provided with cylindrical bores 163 to receive the pivot pins 57which are thereby journaled for rotation.

In this preferred embodiment of the invention, the entire air damper ismade of aluminum except for the swivels 101, 104, etc., which are madeof brass, and also except for the sintered bearings 159. This avoids anyelectrolytic action as may occur when steel and aluminum are usedtogether. The swivels and bearings may, on the other hand, also be madeof aluminum metal.

Referring now to FIG. 8, the preferred method of manufacture andassembly is outlined in block diagram form. The first steps of themethod are to sever predetermined lengths from a long aluminum extrusionto provide the desired number of blades 20. Also, in a like manner asecond long extrusion of aluminum of the cross-sectional shape of thesecond blades 21 is severed to form blades 21 of the predeterminedlength. The frame members 15, 16 and 17 are each severed from a commonlong extrusion of aluminum at predetermined lengths for the height andwidth of the damper to be made. After severing, the damper blades arepierced to provide the apertures for reception of the rivets such asrivets 96 or 113 to attach brackets such as brackets 95, 111, 108, etc.The brackets are riveted to the blades. The slotted pivot pins 57 arepositioned on the ends of the blades with the web 61 inserted into theslots 59 in the pins. The power blade will receive the elongated pivotpin 57A.

Prior to pivotally mounting the blades in the damper frame 14, seals 39and 40 cut to the desired length are inserted into the respectivegrooves 73 of the channel means 33 and 35. A backing strip for theadhesive coating is peeled from the strips, and the adhesive coating isforced against the bottom wall 43 of the respective grooves 73. Wherethe wide channel means 35 cooperates with the bottom shelf 29, a wideseal 40A is adhered to the bottom channel wall 43 for the bottom blade.

The side frame members 17 are notched to provide the openings 51 forreceiving the bearings 159. One of the side frame members 17 is alsopierced to provide the opening 91 for the elongated pivot pin 51A. Theframe members 15, 16 and 17 are pierced near the corners to receiverivets 51. Three of the four frame members are then joined together toform a partial frame, preferably the top and bottom members 15 and 16being joined to one side member 17. With the angles 149 then beingriveted by rivets 151 to form the partial frame, the bearings 159 maythen be slid into place within the openings 51 with slots 161 in thebearings receiving portions of the side shelves 29. Then the respectiveblades may be mounted with their pivot pins 57 inserted into theopenings 163 in the bearings 159. The remaining side frame 17 is thenpositioned with its bearings 159 on the pivot pins 57 and it is joinedto the top and bottom frame by angles 149 and rivets 151.

The shafts 103, 115 and 132 are then connected to the respective swivels101, 104, 117, etc., carried by the various brackets to interconnect theblades 20 and 21 and complete the linkage means 92. With the bladesswung to a closed and nested relationship with one another, the setscrews 102 may be tightened in the swivels to provide the effectivelength for the respective shafts and the angular relationships whichwill cause the wide grooves 73 on the power blade 21 and the otherblades 21 to move to the open position slightly before movement of theblades 20 from the closed position. Conversely, the linkage means 92causes the blades 20 to swing to a closed position and into engagementwith the side shelves 29 before the wide channel means 35 follow to theclosed nested relationship and into engagement with the side shelves asshown in FIG.

From the foregoing it will be seen that air dampers may be provided withmetal blades of unique shape for assuring a nested sealing relationshipwith one another when in a closed position. The air damper may bereadily assembled from a small inventory of metal blades and framemembers for various widths and lengths of air dampers and at a low cost.The blades may be readily positioned in the frame and adjustablyinterconnected to assure the blades will seal with side, top and bottomshelves on the frame and will nest with one another along longitudinallyextending edges thereof when the blades are in a closed position. Whilethe preferred and described embodiment of the inventionis made withextruded aluminum blades and frame members, the invention isnot to be soconstrued as limited to the use of only aluminum metal or to the use ofonly extruded metal blades. Indeed, the air damper blades may be made ofsteel and the frame members made of steel or other metals and still fallwithin the purview of the invention as set forth in the appended claims.

While a preferred embodiment has been shown and described, it will beunderstood that there is no intent to limit the invention by suchdisclosure but, rather, it is intended to cover all modifications andalternate constructions falling within the spirit and scope of theinvention as defined in the appended claims.

What is claimed is:

1. An air damper comprising a frame formed of metal frame members, saidframe having a top and bottom frame member extending parallel to oneanother and a pair of parallel side frame members extending between andjoined to said top and bottom frame members and defining therewith acentral air flow opening, a shelf on each of said frame membersprojecting inwardly from said frame members and extending longitudinallythereof, a first set of metal damper blades each supported at oppositeends on said side frame members and extending longitudinally across theair flow opening and mounted for turning about a pivot axis through acentral portion thereof, a second set of metal blades cooperable withsaid first set of blades with each of said second set of bladesextending longitudinally across the air flow opening and mounted forturning about a pivot axis through a central portion thereof, each ofsaid blades of said first and second sets of blades having side edgeportions for overlapping said shelves on said side frame members whenthe damper blades are in a closed position blocking air flow throughsaid opening, said damper blades mounted in said frame for sealingcooperation with respective shelves of said top and bottom framemembers, means interconnecting said blades of said first and second setsto turn the same in opposite directions between the closed position andopen positions in which said blades of said sets are spaced from eachother to allow air flow through said damper, each of said first set ofblades having longitudinally extending channel means of a predeterminedwidth along each of its longitudinally extending edges, and each ofsecond set of blades having longitudinally extending channel means of awidth wider than the width of said channel means of said first set ofdamper blades, said blades being positioned in said frame to overlap thechannel means of respectively adjacent blades of said first and secondsets to provide a sealing relationship therebetween when said blades arein the closed position, and interconnecting means pivoting said bladeswith narrow channel means to a closed position with said frame and thenpivoting said wider channel means to close on said narrow channel meansto provide a nested sealing relationship between the longitudinal edgesof adjacent blades of said first and second sets of damper blades.

2. An air damper in accordance with claim 1 in which said narrow andwide channels means comprise a groove and a projecting wall defining thebottom of said groove and in which resilient seals are carried in therespective narrow and wide grooves, said wider channel means having wideseals and said narrower channels having narrower seals, said projectingwalls of said narrow channel means nesting in said wide grooves andabutting said wide seals when said blades of said first and second setsare in sealing engagement.

3. An air damper in accordance with claim 2 in which said wide andnarrow seals are flat rectangular strips and are adhesively secured intheir respective channel means.

4. An air damper in accordance with claim 3 in which each of said narrowchannel means has a groove of a predetermined depth therein, and saidnarrow seals have a thickness greater than said groove depth to projecttherefrom for compression against said shelf on said top frame member.

5. An air damper in accordance with claim 1 in which pivot meansincludes slotted pivot pins pivotally mounting said blades on said sideframes, a pair of oppositely directed and longitudinally extending ribmeans are formed on each of said blades for strengthening said bladesagainst bowing, said rib means centering said slotted pins on saiddamper blades and reinforcing the same against tearing by said slottedpins.

6. An air damper in accordance with claim 1 in which each of said bladesexcept the uppermost blade is symmetrical about its pivot axis, saiduppermost blade having an upper portion thereof of a width differentthan the width of a lower portion thereof, said upper portion of saiduppermost blade extending to said upper shelf when the blades are in theclosed position.

7. An air damper in accordance with claim 1 in which said side, top andbottom frame members have identical cross sections and in which bracketmeans are provided at the spaced corners ofsaid frame to interconnectsaid side frame members with said top and bottom frame members and inwhich outer portions of said fasteners are accommodated with grooves inthe exterior walls of said frame members to fasten said bracket means tosaid frame members.

8. An extruded aluminum damper blade for use in an air damper comprisinga central section at a central axis about which the blade will bepivoted, oppositely directed rib means projecting outwardly from saidblades and spaced from said axis to reinforce the central section of theblade against bending, said central section and said rib means defininga cross-section of substantially I beam shape, longitudinally extendingchannel means formed on each of the longitudinally extending edges ofsaid blade, said channel means being identical in size and shape, saidblade having a first wide planar portion extending from one side of saidsection in a plane parallel to and spaced from the central pivot axis,and a second wide planar portion extending from the other side of saidcentral section and in a plane parallel to and spaced from the plane ofsaid first wide planar portion, said channel means being joined to theouter edges of said wide planar portions.

9. An air damper blade in accordance with claim 8 in which each of saidchannel means is substantially rectangular in cross section andcomprises a pair of spaced, parallel longitudinally extending side wallsdefining the sides of the channel means, and a flat bottom wallsubstantially normal to and spanning said side walls and defining thebottom of said channel means.

10. An air damper comprising a metal frame and metal damper blades, saidframe having parallel top and bottom frame members, parallel side framemembers spacing said top and bottom members and extending therebetweenand defining therewith a central air flow opening, said frame memberseach having a longitudinally extending shelf projecting inwardlytherefrom, said damper blades including first and second sets of bladespivotally mounted in said air damper, each of said damper blades havinga length longer than the distance between inner edges of said shelves onsaid side members, pivot means for said blades mounted in openings insaid side member shelves, an offset portion at each end of said bladeprojecting through shelf openings, each of said blades having marginalside edges thereof in sealing engagement with opposite sides of saidshelves of said side members, said first set of blades havinglongitudinally extending channel means therein of a predetermined width,a resilient seal carried in each of said channel means, said second setof damper blades alternating with damper blades of said first set ofdamper blades and pivotally mounted to said side frame members forturning in a direction opposite to direction of turning of said firstset of blades, said second blades having longitudinally extendingchannel means of a width wider than said predetermined width forreceiving in nesting relationship the channel means of the first set ofblades when the blades are in a closed position blocking air flowthrough the opening, said narrow channel means having a projectingportion formed along one side thereof, resilient seals carried by saidwide channel means for sealing engagement with a projecting portion ofthe narrow channel means of the first set of blades, and meansinterconnecting said first and second set of blades to pivot said narrowseals against said shelves on said side members and subsequently topivot said wide seals against said projecting portions of said narrowchannel means to nest said narrow and wide channel means when saidblades of said first and second sets are in the closed position.

1. An air damper comprising a frame formed of metal frame members, saidframe having a top and bottom frame member extending parallel to oneanother and a pair of parallel side frame members extending between andjoined to said top and bottom frame members and defining therewith acentral air flow opening, a shelf on each of said frame membersprojecting inwardly from said frame members and extending longitudinallythereof, a first set of metal damper blades each supported at oppositeends on said side frame members and extending longitudinally across theair flow opening and mounted for turning about a pivot axis through acentral portion thereof, a second set of metal blAdes cooperable withsaid first set of blades with each of said second set of bladesextending longitudinally across the air flow opening and mounted forturning about a pivot axis through a central portion thereof, each ofsaid blades of said first and second sets of blades having side edgeportions for overlapping said shelves on said side frame members whenthe damper blades are in a closed position blocking air flow throughsaid opening, said damper blades mounted in said frame for sealingcooperation with respective shelves of said top and bottom framemembers, means interconnecting said blades of said first and second setsto turn the same in opposite directions between the closed position andopen positions in which said blades of said sets are spaced from eachother to allow air flow through said damper, each of said first set ofblades having longitudinally extending channel means of a predeterminedwidth along each of its longitudinally extending edges, and each ofsecond set of blades having longitudinally extending channel means of awidth wider than the width of said channel means of said first set ofdamper blades, said blades being positioned in said frame to overlap thechannel means of respectively adjacent blades of said first and secondsets to provide a sealing relationship therebetween when said blades arein the closed position, and interconnecting means pivoting said bladeswith narrow channel means to a closed position with said frame and thenpivoting said wider channel means to close on said narrow channel meansto provide a nested sealing relationship between the longitudinal edgesof adjacent blades of said first and second sets of damper blades.
 2. Anair damper in accordance with claim 1 in which said narrow and widechannels means comprise a groove and a projecting wall defining thebottom of said groove and in which resilient seals are carried in therespective narrow and wide grooves, said wider channel means having wideseals and said narrower channels having narrower seals, said projectingwalls of said narrow channel means nesting in said wide grooves andabutting said wide seals when said blades of said first and second setsare in sealing engagement.
 3. An air damper in accordance with claim 2in which said wide and narrow seals are flat rectangular strips and areadhesively secured in their respective channel means.
 4. An air damperin accordance with claim 3 in which each of said narrow channel meanshas a groove of a predetermined depth therein, and said narrow sealshave a thickness greater than said groove depth to project therefrom forcompression against said shelf on said top frame member.
 5. An airdamper in accordance with claim 1 in which pivot means includes slottedpivot pins pivotally mounting said blades on said side frames, a pair ofoppositely directed and longitudinally extending rib means are formed oneach of said blades for strengthening said blades against bowing, saidrib means centering said slotted pins on said damper blades andreinforcing the same against tearing by said slotted pins.
 6. An airdamper in accordance with claim 1 in which each of said blades exceptthe uppermost blade is symmetrical about its pivot axis, said uppermostblade having an upper portion thereof of a width different than thewidth of a lower portion thereof, said upper portion of said uppermostblade extending to said upper shelf when the blades are in the closedposition.
 7. An air damper in accordance with claim 1 in which saidside, top and bottom frame members have identical cross sections and inwhich bracket means are provided at the spaced corners of said frame tointerconnect said side frame members with said top and bottom framemembers and in which outer portions of said fasteners are accommodatedwith grooves in the exterior walls of said frame members to fasten saidbracket means to said frame members.
 8. An extruded aluminum damperblade for use in an air damper comprising a central section at a centraLaxis about which the blade will be pivoted, oppositely directed ribmeans projecting outwardly from said blades and spaced from said axis toreinforce the central section of the blade against bending, said centralsection and said rib means defining a cross-section of substantially Ibeam shape, longitudinally extending channel means formed on each of thelongitudinally extending edges of said blade, said channel means beingidentical in size and shape, said blade having a first wide planarportion extending from one side of said section in a plane parallel toand spaced from the central pivot axis, and a second wide planar portionextending from the other side of said central section and in a planeparallel to and spaced from the plane of said first wide planar portion,said channel means being joined to the outer edges of said wide planarportions.
 9. An air damper blade in accordance with claim 8 in whicheach of said channel means is substantially rectangular in cross sectionand comprises a pair of spaced, parallel longitudinally extending sidewalls defining the sides of the channel means, and a flat bottom wallsubstantially normal to and spanning said side walls and defining thebottom of said channel means.
 10. An air damper comprising a metal frameand metal damper blades, said frame having parallel top and bottom framemembers, parallel side frame members spacing said top and bottom membersand extending therebetween and defining therewith a central air flowopening, said frame members each having a longitudinally extending shelfprojecting inwardly therefrom, said damper blades including first andsecond sets of blades pivotally mounted in said air damper, each of saiddamper blades having a length longer than the distance between inneredges of said shelves on said side members, pivot means for said bladesmounted in openings in said side member shelves, an offset portion ateach end of said blade projecting through shelf openings, each of saidblades having marginal side edges thereof in sealing engagement withopposite sides of said shelves of said side members, said first set ofblades having longitudinally extending channel means therein of apredetermined width, a resilient seal carried in each of said channelmeans, said second set of damper blades alternating with damper bladesof said first set of damper blades and pivotally mounted to said sideframe members for turning in a direction opposite to direction ofturning of said first set of blades, said second blades havinglongitudinally extending channel means of a width wider than saidpredetermined width for receiving in nesting relationship the channelmeans of the first set of blades when the blades are in a closedposition blocking air flow through the opening, said narrow channelmeans having a projecting portion formed along one side thereof,resilient seals carried by said wide channel means for sealingengagement with a projecting portion of the narrow channel means of thefirst set of blades, and means interconnecting said first and second setof blades to pivot said narrow seals against said shelves on said sidemembers and subsequently to pivot said wide seals against saidprojecting portions of said narrow channel means to nest said narrow andwide channel means when said blades of said first and second sets are inthe closed position.